<!DOCTYPE html>
<html class="reftest-wait">
<title>View transitions: Modify style via CSSOM</title>
<link rel="help" href="https://drafts.csswg.org/css-view-transitions-1/">
<link rel="author" href="mailto:bokan@chromium.org">
<link rel="match" href="modify-style-via-cssom-ref.html">
<script src="/common/reftest-wait.js"></script>
<style>
#box {
  width: 100px;
  height: 100px;
  background: limegreen;
}
html::view-transition-group(root) {
  animation-duration: 300s;
}
html::view-transition-new(root) {
  animation: none;
  opacity: 0;
}
html::view-transition-old(root) {
  animation: none;
  opacity: 1;
}
</style>
<div id="box"></div>

<script>
failIfNot(document.startViewTransition, "Missing document.startViewTransition");

function rAF() {
  return new Promise(resolve => requestAnimationFrame(resolve));
}

async function runTest() {
  await document.startViewTransition().ready;
  await rAF();
  await rAF();

  // Once the animation is running, ensure modifying style via CSSOM is
  // effective.
  const cssSheet = new CSSStyleSheet();
  cssSheet.replaceSync(`::view-transition-old(root) {
    transform: translateY(100px);
  }`);
  document.adoptedStyleSheets = [cssSheet];

  await rAF();
  takeScreenshot();
}
onload = () => requestAnimationFrame(() => requestAnimationFrame(runTest));
</script>
</html>
